Display 0 - 1000 - 0 each on a separate line

Question

I've tried this question on two forums and have been told this is the best place for this type of question. I'm trying to print from 0 to 1000 then back to 0 again (and all numbers in-between), printing 1000 only once. Also, each number must be on a separate line using vanilla PHP.

My current code is 60 characters long. Is there a way to do the same thing but in less characters?

PHP, 60 bytes

echo implode("<p>",array_merge(range(0,999),range(1000,0)));

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Answer 1

PHP, 38 bytes

for(;$i-=1|$x|=$i/1001;)echo~$i,"<p>";

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A one-byte improvement by JoKing. The idea is that by decrementing $i instead of incrementing it, we can save on the minus in the 1|-$x construction by having $x become -1 instead of 1 as a signal. This is achieved by using $i/1001, which is 0 if $i>-1001 and -1 otherwise. This would break even if not for the fact we can now use ~$i instead of $i-1.

PHP, 39 bytes

for(;$i+=1|-$x|=$i>1e3;)echo$i-1,"<p>";

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In collaboration with primo on the code.golf discord.

The idea is to have a signal variable $x that is zero until $i hits 1000 then is 1 afterwards. We use the bitwise construction 1|-$x which is a shorter version of $x ? -1 : 1 to select whether to go upwards or downwards.

Answer 2

PHP,  56  49 bytes

Saved 7 bytes thanks to @Sisyphus and @xnor

My PHP is rusty, but here is a first attempt.

for(;$n<2e3;)echo 1e3-abs(1e3-$n++),'<p>';echo 0;

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47 bytes

A shorter version suggested by @Neil:

echo 0;for(;$n<2e3;)echo'<p>',min(++$n,2e3-$n);

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43 bytes

If the output can end with an extra <p>:

for(;$n<2001;)echo 1e3-abs(1e3-$n++),'<p>';

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Answer 3

PHP, 51 bytes

echo join("<p>",[...range(0,999),...range(1e3,0)]);

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There's already shorter versions, but I just wanted to show the OP how the original code can be shortened with the old alias join and the spread operator that is now available in PHP

Depending on your rules, even shorter:

49 bytes with <?=

<?=join("<p>",[...range(0,999),...range(1e3,0)]);

or even 47 with a literal new line, if your output can be wrapped in <pre><code>

<?=join("
",[...range(0,999),...range(1e3,0)]);